Abstract
Abstract. Lakes act as important sinks for inorganic and organic sediment components. However, investigations of sedimentary carbon budgets within glacial lakes are currently absent from Arctic Siberia. The aim of this paper is to provide the first reconstruction of accumulation rates, sediment and carbon budgets from a lacustrine sediment core from Lake Rauchuagytgyn, Chukotka (Arctic Siberia). We combined multiple sediment biogeochemical and sedimentological parameters from a radiocarbon-dated 6.5 m sediment core with lake basin hydroacoustic data to derive sediment stratigraphy, sediment volumes and infill budgets. Our results distinguished three principal sediment and carbon accumulation regimes that could be identified across all measured environmental proxies including early Marine Isotope Stage 2 (MIS2) (ca. 29–23.4 ka cal BP), mid-MIS2–early MIS1 (ca. 23.4–11.69 ka cal BP) and the Holocene (ca. 11.69–present). Estimated organic carbon accumulation rates (OCARs) were higher within Holocene sediments (average 3.53 g OC m−2 a−1) than Pleistocene sediments (average 1.08 g OC m−2 a−1) and are similar to those calculated for boreal lakes from Quebec and Finland and Lake Baikal but significantly lower than Siberian thermokarst lakes and Alberta glacial lakes. Using a bootstrapping approach, we estimated the total organic carbon pool to be 0.26 ± 0.02 Mt and a total sediment pool of 25.7 ± 1.71 Mt within a hydroacoustically derived sediment volume of ca. 32 990 557 m3. The total organic carbon pool is substantially smaller than Alaskan yedoma, thermokarst lake sediments and Alberta glacial lakes but shares similarities with Finnish boreal lakes. Temporal variability in sediment and carbon accumulation dynamics at Lake Rauchuagytgyn is controlled predominantly by palaeoclimate variation that regulates lake ice-cover dynamics and catchment glacial, fluvial and permafrost processes through time. These processes, in turn, affect catchment and within-lake primary productivity as well as catchment soil development. Spatial differences compared to other lake systems at a trans-regional scale likely relate to the high-latitude, mountainous location of Lake Rauchuagytgyn.
Highlights
Lakes represent key sentinels of environmental change and can respond rapidly to changes in environmental conditions (Adrian et al, 2009)
Comparison of hydroacoustic with lithological data and boundaries from core EN18218 allow the subdivision of basin infill into two acoustic units (AU1 and AU2) corresponding with sediments deposited within lithological units I (AU1) and II and III (AU2) (Table 2)
Basal structures observed within hydroacoustic data within the lower portion of AU2 may suggest a mixed origin of the coarse sediment that may be related to fluvial or possibly glaciofluvial activity within the basin that subsequently influenced basin sediment distributions
Summary
Lakes represent key sentinels of environmental change and can respond rapidly to changes in environmental conditions (Adrian et al, 2009). Vyse et al.: Sediment and carbon accumulation in a glacial lake in Chukotka from atmospheric deposition and as such gradually accumulate sediment mass over time (Dietze et al, 2014; Hinderer and Einsele, 2001). They constitute a significant net sink of carbon, as they can accumulate organic and inorganic carbon within their sediments derived from allochthonous (lake external) and autochthonous (lake internal) pathways (Ferland et al, 2012; Dean and Gorham 1998; Kortelainen et al, 2004; Sobek et al, 2014). Inland waters can act as major sources of the greenhouse gases CO2 and CH4 and thereby contribute further to global climate change (Anthony et al, 2014)
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